Various types of microphones have been used in various applications through the years. Microphones typically receive acoustic energy and convert this acoustic energy into a voltage. This voltage can be further processed for other applications or purposes. For example, in a hearing aid system the microphone may receive acoustic energy, convert the acoustic energy to voltages, amplify or otherwise process the voltages and present the now-amplified acoustic energy to a user or wearer of the hearing aid. Microphones in cellular phones typically receive the sound energy, convert this energy into a voltage, and this voltage can be further processed for use in the cellular phone or for transmission. Microphones are used in other applications as well.
An interface is often used between the microphone and further processing functions and this interface sometimes employs analog-to-digital conversion circuitry. In particular, this circuitry converts analog signals produced by the microphone into digital signals so that further processing can be performed. This circuitry also has operational limits such that if too much voltage and/or current is applied, it will not function properly.
Today's microphones produce increasingly higher amounts of energy. For example, microphones in cellular phones may be employed to capture not only normal conversations but louder (i.e., high energy sounds) such as music (e.g., from concerts) or the like. These high energy signals produce increased amounts of energy that are eventually presented as high voltages to the interface circuits mentioned above. Unfortunately, the heightened voltage levels often overwhelm the interface circuits. For example, when the interface circuitry includes analog-to-digital circuits that deploy amplifier stages, the amplifier stages can become saturated and the system may then not function properly.
In another example, MEMS microphones often have an operating range that is higher than the interface circuitry. For example, MEMS microphones may be capable of processing signals with 140 dB MAX SPL. Unfortunately, present interfaces handle a substantial lesser amount of energy (e.g., 120 db MAX SPL). This fact leads to wasted capacity that can never be utilized by the user or the system.
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